Appeal 33708

2023 ORSC R302.2.8.2

ORSC R302.2.8.2 Cantilevered living areas

Cantilevered living areas shall be protected by one of the following methods

1. Where one cantilever is adjacent to another cantilever, and both are less than 3 feet from the common property line, a single 1-hour fire-resistance rated townhouse separation wall shall be provided for each cantilever. The townhouse separation walls shall extend to the furthest point where the cantilevers are adjacent.
2. Where one cantilever abuts another adjacent cantilever at a common property line, either two 1-hour fire-resistance rated walls or one ‘modified’ 2-hour fire-resistance rated common townhouse separation wall shall be provided. The townhouse separation wall shall extend to the furthest point where both cantilevers are adjacent.
3. Where there is one cantilever within 3 feet of the common property line and no adjacent cantilever less than 3 feet from the common property line, a 1-hour fire-resistance rated exterior wall shall be provided. The exterior wall shall extend to the furthest point of the cantilever.

The fire-resistance rated walls required in item 1-3 shall be continuous from the foundation to the roof sheathing when the roof/ceiling assembly is constructed in accordance with Section R302.2.6.1. When the roof/ceiling assembly is not constructed in accordance with Section R302.2.6.1, the wall shall terminate in a parapet constructed in accordance with Section R302.2.5.

Allow 3rd floor cantilever that abuts another adjacent cantilever at a common property line with a 2-hour modified common townhouse separation wall to the underside of the cantilever floor assembly and 2-hour rated floor/ceiling assembly for the cantilever floor.

The Tenino townhouses are 3 story townhouses located at: 1. 1521 SE Tenino St

1. 1523 SE Tenino St
2. 1527 SE Tenino St
3. 1529 SE Tenino St

using a ‘modified’ 2-hour rated separation wall between units. The townhouses are non-sprinklered per ORSC R302.2.

The townhouses with abutting 3rd floor cantilevered living areas will meet the requirements of ORSC R302.2.8.2, item 2, except the 2-hour rated wall will not go down to the foundation. Equivalent protection will be provided with a 2-hour rated floor/ceiling assembly on the cantilevered living area floor. The underside of the floor assembly will be covered with a non-combustible cementitious weather protection panel.

The 2-hour rated floor protection provides equivalent protection for fire migrating from one townhouse to the next for a period of 2 hours, equivalent to the rating of the separation wall between townhouse units.

The 2-hour rated floor/ceiling assembly will be rated as required pr ASTM E119 to prevent flame penetration and heat migration from a fire into the cantilevered living area.

The siding on the townhouses is cementitious lap siding to prevent fire migration on the exterior of the building. The proposed design also provides equivalent protection to ORSC 302.2.8.2, exception 2, which only requires a 1-hour rated wall under the cantilevered living area to provide a 1-hour rated soffit assembly for 4’ beyond the common property line. Exception 2 is not possible for the design since a window is within 4’ of the common property line.

The same plan with 4’ wide cantilevered living area configuration has been permitted without a rated cantilevered floor assembly or a sprinkler system at two projects by the same builder at 8949 N Kellogg St and 6401 E Burnside St.